This invention relates to a magnetic disc cartridge, and more particularly to a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and a pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves and to a method of manufacturing the same. This invention also relates to a method of cleaning the liners.
In a magnetic disc cartridge comprising a disc-like recording medium supported for rotation in a casing formed of upper and lower shell halves, a pair of liners formed of nonwoven fabric or the like are generally fixed to the inner surfaces of the upper and lower shell halves, respectively.
The liners are for protecting the recording medium and are formed of nonwoven fabric or the like of rayon or the like in a predetermined shape. The liners are fixed to the inner surfaces of the upper and lower shell halves by welding such as ultrasonic welding.
Each liner is generally octagonal in contour and is provided with a central opening and a slit-like cutaway portion which is opposed to the magnetic head insertion opening formed in the corresponding shell half.
When welding the liner to the shell half, a welding horn is pressed against the liner placed on the inner surface of the shell half and heat or ultrasonic vibration is applied to the welding horn, thereby fusing the inner surface of the shell half to the liner.
For example, there has been proposed in Japanese Patent Application No. 9(1997)-296838, a method of fixing a liner to the inner surface of a shell half by ultrasonic welding in which an energy director in the form of a protrusion is formed in a predetermined pattern on the inner surface of the shell half, the liner is placed on the energy director, and an ultrasonic welding horn is pressed against the liner so that the energy director is fused to the liner.
In the past, the liner is fixed to the shell half only at a part of its peripheral edge. Accordingly the non-fixed part of the peripheral edge and/or the central portion of the liner is in a floating condition and can be brought into contact with the recording medium. However, recently, as the recording capacity of the recording medium increases, it becomes necessary to rotate the recording medium at a higher speed. When the recording medium rotated at a high speed is constantly in contact with the liner, contaminants can be produced, for instance, by separation of fibers from the liner. When such contaminants adhere to the recording medium and/or the magnetic head, recording and reproducing performance can be adversely affected, recording medium driving torque can be increased, and the recording medium can wobble during rotation. Accordingly, there is a tendency to reduce contact of the liner to the recording medium.
Further since the liner is stamped out from a sheet of unwoven fabric, when the liner is not welded over its entire peripheral edge, cut fibers can drop from its peripheral edge and can adhere to the surface of the recording medium to cause drop out.
Further since the liner is formed of a hygroscopic material such as rayon, when the central portion of liner is not fixed to the inner surface of the shell half, the liner is deformed in such a manner that the central portion bulges upward due to hygroscopicity under the conditions of 60xc2x0 C. in temperature and 90% in humidity. When the liner is thus deformed, the bulging portion is brought into contact with the recording medium which rotating at a high speed, which gives rise to the aforesaid problems.
In view of the foregoing observations and description, the primary object of the present invention is to provide a method of manufacturing a magnetic disc cartridge which can prevent fibers from dropping from the peripheral edges of the liners and can prevent the liners from constantly contacting with the rotating recording medium.
Another object of the present invention is to provide a method of manufacturing a magnetic disc cartridge which can prevent the central portions of the liners from bulging into contact with the recording medium even if they absorb moisture.
Still another object of the present invention is to provide a magnetic disc cartridge in which the recording medium can be effectively cleaned by the liners without substantially increasing the recording medium drive torque.
Still another object of the present invention is to provide a method of cleaning a liner of a magnetic disc cartridge which can effectively remove dust and free fibers from the liner without damaging the casing and/or the recording medium.
In accordance with a first aspect of the present invention, there is provided a method of manufacturing a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and an octagonal liner fixed to each of the inner surfaces of the upper and lower shell halves by use of a welding horn, the liner having a substantially octagonal outer contour defined by an outer peripheral edge, a central opening defined by an inner peripheral edge, and a slit-like cutaway portion defined by a pair of linear edges extending between the outer peripheral edge and the inner peripheral edge, which method is characterized in that
the welding horn has a welding face (the front end face) whose outer contour is an octagon conforming to the outer contour of the liner so that the liner is welded to the inner surface of the shell half substantially over the entire outer peripheral edge thereof.
It is preferred that the liner be welded to the inner surface of the shell half substantially over the entire outer peripheral edge, the inner peripheral edge and the linear edges.
The liner need not be welded to the inner surface of the shell half continuously over the edges described above but may be welded at a plurality of spots along the edges provided that the spots are sufficiently closely arranged to prevent fibers from dropping from the edges.
The liner may be welded to the inner surface of the shell half by forming an energy director protrusion on the inner surface of the shell half along the edge or edges of the liner to be welded or by forming a protrusion on the welding face of the welding horn along the edge or edges of the liner to be welded.
It is preferred that the liner be electrostatically processed to attract and hold fiber dust.
In accordance with a second aspect of the present invention, the surface of an edge portion of the liner facing the recording medium is made more distant from the recording medium than the other part of the liner and fixing agent is caused to soak into the edge portion and is solidified there.
The surface of an edge portion of the liner facing the recording medium may be made more distant from the recording medium than the other part of the liner, for instance, by forming a recess in the inner surface of the shell half or by compressing the part of the liner with the inner surface of the shell half held flat.
The fixing agent may be adhesive applied to the liner or may be molten resin obtained by fusing the shell half by applying heat or ultrasonic vibration.
In accordance with a third aspect of the present invention, there is provided a method of manufacturing a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and a liner fixed to each of the inner surfaces of the upper and lower shell halves by ultrasonic welding by use of an ultrasonic welding horn, the liner having an outer contour defined by an outer peripheral edge, a central opening defined by an inner peripheral edge, and a slit-like cutaway portion defined by a pair of linear edges extending between the outer peripheral edge and the inner peripheral edge, which method is characterized in that said ultrasonic welding horn is provided with a welding pattern in the form of a protrusion pattern formed on a welding face thereof over the entire welding area in which the ultrasonic welding horn is brought into contact with the liner, and the liner is welded to the inner surface of the shell half over the entire area of the liner along the welding pattern.
The welding pattern may be a longitudinal or transverse stripe pattern, a grid pattern, a radial pattern or the like. It is preferred that the welding pattern be uniformly spaced over the entire area of the liner opposed to the recording area of the recording medium. Further the welding pattern may be of the same form over the entire area of the liner or may be of different forms between the edge portion of the liner along the edges of the liner and the inner portion of the liner opposed to the recording area of the recording medium.
In accordance with the method of the third aspect of the present invention, the liner is welded to the inner surface of the shell half along the welding pattern over the entire area of the liner and accordingly the liner cannot largely bulge even if the liner absorbs moisture, whereby the liner is prevented from contacting the recording medium rotating at a high speed. Accordingly, production of contaminants and increase of the recording medium driving torque can be suppressed, and the recording medium can be prevented from wobbling during rotation, whereby good recording and reproducing characteristics can be ensured and the recording medium can be stably rotated at a high speed.
In the case where the energy director in the form of a protrusion formed on the inner surface of the shell half is fused, fused components can penetrate through the liner up to the surface thereof and can be solidified there. When the recording medium is brought into contact the solidified components, recording quality can be deteriorated. To the contrast, when the ultrasonic welding horn is provided with the welding pattern in the form of a protrusion pattern and the inner surface of the shell half is flat, fused components of the shell half less penetrates through the liner up to the surface thereof and accordingly even if the solidified components of the shell half is brought into contact with the recording medium, the recording quality is less affected.
In accordance with a fourth aspect of the present invention, there is provided a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and a pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves, each of the upper and lower shell halves being provided with a magnetic head insertion opening and each of the liners having a slit-like cutaway portion opposed to the magnetic head insertion opening of the corresponding shell half, wherein the improvement comprises that
a part of each of the liners extending upstream from the edge of the cutaway portion as seen in the direction of rotation of the recording medium is not fixed to the inner surface of the shell half so that the unfixed part can float from the inner surface of the shell half into contact with the surface of the recording medium.
It is preferred that at least an edge portion of the part of the unfixed part of the liner to be brought into contact with the recording medium be subjected to fiber fixing treatment for preventing hairiness and separation of fibers. Such fiber fixing treatment may involve, for instance, application of adhesive, or heat fusing. The edge portion of the part of the unfixed part of the liner may be further subjected to chemical dust treatment for enhancing dust adsorbability.
It is preferred that the unfixed part be formed within 60xc2x0 from the center of the magnetic head insertion window as measured in the direction of rotation of the recording medium in view of ensuring sufficient dust wiping action without excessively increasing the recording medium drive resistance.
When a resilient member or a rigid member is disposed between the unfixed part and the inner surface of the shell half to urge the unfixed part toward the recording medium, the unfixed part can be surely brought into contact with the surface of the recording medium and dust wiping action is enhanced. For example, the resilient member may be formed of the same material as the liner and the rigid member may be in the form of a rib formed on the inner surface of the shell half.
In accordance with a fifth aspect of the present invention, there is provided a method of cleaning a liner of a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and a pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves, which method comprising the steps of
positioning each of the shell halves bearing thereon the liner fixed thereto with the surface of the liner opposed to a front end face of an ultrasonic welding horn at a predetermined space therefrom,
vibrating the liner by ultrasonic wave radiated from the front end face of the ultrasonic welding horn, and
blowing an air flow against the surface of the liner.
It is preferred that the distance between the liner and the front end face of the ultrasonic welding horn be an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air.
Further the ultrasonic welding horn may be moved relatively to the liner in a range including an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air.
In accordance with a sixth aspect of the present invention, there is provided a method of cleaning a liner of a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and a pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves, which method comprising the steps of
bringing each of the shell halves bearing thereon the liner fixed thereto into contact with an ultrasonic welding horn,
vibrating the liner by ultrasonic wave applied to the shell half from the ultrasonic welding horn, and
blowing an air flow against the surface of the liner.
It is preferred that the shell half be supported by an elastic means disposed on the side of the shell half remote from the ultrasonic welding horn.
The shell half may be placed on a support table supported by an air cylinder.